Reactive oxygen intermediates mediate angiotensin II-induced c-Jun.c-Fos heterodimer DNA binding activity and proliferative hypertrophic responses in myogenic cells
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P L Puri1, M L Avantaggiati, V L Burgio
1Fondazione Andrea Cesalpino, University of Rome La Sapienza, Italy.
Abstract:
Angiotensin II (Ang-II) receptor engagement activates many immediate early response genes in both vascular smooth muscle cells and cardiomyocytes whether a hyperplastic or hypertrophic response is taking place. Although the signaling pathways stimulated by Ang-II in different cell lines have been widely characterized, the correlation between the generation of different second messengers and specific physiological responses remains relatively unexplored. In this study, we report how in both C2C12 quiescent myoblasts and differentiated myotubes Ang-II significantly stimulates AP1-driven transcription and c-Jun.c-Fos heterodimer DNA binding activity. Using a set of different protein kinase inhibitors, we could demonstrate that Ang-II-induced increase in AP1 binding is not mediated by the cAMP-dependent pathway and that both protein kinase C and tyrosine kinases are involved. The observation that in quiescent myoblasts Ang-II increase of AP1 binding and induction of DNA synthesis and, in differentiated myotubes, Ang-II stimulation of protein synthesis are abolished by the cysteine-derivative and glutathione precursor N-acetyl-L-cysteine strongly suggests a role for reactive oxygen intermediates in the intracellular transduction of Ang-II signals for immediate early gene induction, cell proliferation, and hypertrophic responses.
Insights
Angiotensin II (Ang-II) stimulates immediate early gene responses in muscle cells. Reactive oxygen intermediates play a key role in Ang-II signaling for cell proliferation and hypertrophy.
Area of Science:
- Cellular and Molecular Biology
- Cardiovascular Research
- Biochemistry
Background:
- Angiotensin II (Ang-II) receptor activation triggers immediate early response genes in vascular smooth muscle cells and cardiomyocytes.
- Signaling pathways of Ang-II are well-characterized, but the link between second messengers and physiological outcomes needs further exploration.
Purpose of the Study:
- To investigate the role of reactive oxygen intermediates (ROIs) in Angiotensin II-induced signaling pathways.
- To elucidate the specific signaling mechanisms linking Ang-II to immediate early gene induction, cell proliferation, and hypertrophy.
Main Methods:
- Utilized C2C12 myoblasts and differentiated myotubes to study Ang-II effects.
- Employed protein kinase inhibitors and N-acetyl-L-cysteine to dissect signaling pathways.
- Assessed AP1-driven transcription and c-Jun/c-Fos heterodimer DNA binding activity.
Main Results:
- Ang-II significantly stimulated AP1-driven transcription and c-Jun/c-Fos DNA binding in both myoblasts and myotubes.
- Ang-II-induced AP1 binding was independent of the cAMP pathway but involved protein kinase C and tyrosine kinases.
- N-acetyl-L-cysteine abolished Ang-II's effects on AP1 binding, DNA synthesis, and protein synthesis.
Conclusions:
- Reactive oxygen intermediates are crucial for intracellular signal transduction of Ang-II.
- ROIs mediate Ang-II's effects on immediate early gene induction, cell proliferation, and hypertrophic responses in muscle cells.